Objectives of this study will be to obtain information about protein synthesis in the hamster cheek pouch in relation to epithelial cell differentiation, under normal and altered conditions. 1) Particular attention will be paid to the role of protein(s) synthesized in the upper cell layers of the epithelium and how they relate to the cell organelles with particular attention to the keratohyalin graules. 2) Correlative histochemical, light and electron microscopic autoradiographic studies will be carried out to identify the sites of active protein synthesis. For this purpose a series of tritiated amino acids including histidine and cystine and H3-uridin will be used. 3) Studies to determine the biochemical nature of the proteins in relation to the keratohyaline granules will be also be conducted. 4) The nature of the epithelia altered by dimethylbenz(a)-anthracene (DMBA) will also be characterized by the above mentioned techniques and compared with normal epithelia. 5) Attempts will be made to define the differences between normal and altered human epithelia in the hopes of establishing data that may be used as a diagnostic parameter. 6) Detailed ultrastructural characterization of the normal hamster cheek pouch epithelium will be carried out. If the objectives of this study can be achieved, then a significant step can be made toward understanding the mechanisms of differentiation of epithelium in relation to keratinization.